In the present work the behavior of different substituted iminic bonds toward the oxidative action of 3-chloroperbenzoic acid is reported. The C=N bond was or was not oxidized to oxaziridines, amides, oximes, nitroso-, nitro-, and azodioxy compounds depending on the substituents at the iminic group and on the imine/MCPBA stoichiometric ratio

CANNAZZA, Giuseppe

Carrozzo,

Citti, Ca

Falcicchio, A

M. M.

Mansueto, R

Rosato, F

Troisi, L.

Archivio istituzionale della ricerca - Università di Modena e Reggio Emilia

LETTER ▌53letterOn the Oxidation of Different Iminic Bonds by Excess of 3-Chloroperbenzoic AcidOxidation of Different Iminic BondsLuigino Troisi,*a Marina M. Carrozzo,a Cinzia Citti,a Aurelia Falcicchio,b Rosmara Mansueto,a Francesca Rosato,a Giuseppe Cannazzaca Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Via Prov. le Lecce-Monteroni, 73100 Lecce, ItalyFax +39(0832)298732; E-mail: luigino.troisi@unisalento.itb Istituto di Cristallografia (IC-CNR) , Via Amendola 122/o, 70125 Bari, Italyc Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, via Campi 183, 41125 Modena, ItalyReceived: 19.10.2012; Accepted after revision: 15.11.2012Abstract: In the present work the behavior of different substitutediminic bonds toward the oxidative action of 3-chloroperbenzoicacid is reported. The C=N bond was or was not oxidized to oxaziri-dines, amides, oximes, nitroso-, nitro-, and azodioxy compoundsdepending on the substituents at the iminic group and on theimine/MCPBA stoichiometric ratio.Key words: imines, oxidation, oxaziridines, C-nitroso compound,oximesAlthough the reduction1 and hydrolysis2 of imines hasbeen largely studied, only a few publications report its be-havior toward oxidizing agents. It has been reported thatbenzylidene alkylamines lead to the corresponding oxa-ziridines by stoichiometric oxidation with peracids,3 ureahydrogen peroxide,4 and cobalt-mediated molecularoxygen5 (Scheme 1).Scheme 1  Synthetic methodology for oxaziridine generationA number of thermally stable oxaziridines, obtained byoxidation of benzylidene alkylamines,6 have been em-ployed both as oxygenating and/or aminating agents ofnucleophilic species7 and as reagents in cycloaddition re-actions with heterocumulenes,8 alkenes,9 alkynes,10 andnitriles.11 Reports of reactions of imines with excessMCPBA are scarce. Previously, we have reported that theoxidation of benzylidene alkylamines 1–3 by 1.1 mmol ofMCPBA in CH2Cl2 solution led to oxaziridines 1a–3a ingood yields (>90%),12 while nitroso compounds 1b–3brapidly dimerized to azodioxy compounds 1c–3c andwere obtained employing 2.2 mmol of MCPBA (Scheme2). Furthermore compounds 2b, 3b, 2c, and 3c, having ahydrogen at the α position of R1, undergo isomerizationinto oximes 2d and 3d by heating in toluene solution.Moreover, the azodioxy dimer 3c was obtained in quanti-tative yield by reaction of 1.1 mmol MCPBA with the iso-lated oxaziridine 3a.The same result was obtained on oxidizing the cyclic im-ine 3,4-dihydro-2H-pyrrole 4 with 1.1 mmol of MCPBA;the condensed oxaziridine 4a (yield 98%) was obtained inthis case. Product 4a was subsequently oxidized into ni-troso compound 4b that rapidly dimerized to azoxydimer4c when a further 1.1 mmol of MCPBA were added. Fur-thermore, on heating 4c in toluene (80 °C), 4d was ob-tained (yield 80%, Scheme 3).12Continuing our studies on the oxidation of imines withMCPBA we have discovered outcomes strongly depen-dent on the C=N bond substituents. Due to the lowerbasicity of the nitrogen in 5–7 with respect to compounds1–4, the second oxygen transfer on oxaziridines 5a–7a,formed on initial oxidation, did not take place. Instead,N,N-diarylamides 8–10 were obtained both with 1.1 mmolor 2.2 mmol of peracid, after a carbon–nitrogen migrationof the aryl group (Scheme 4). Amides were also obtainedin reactions of imines with sodium perborate13 or withMCPBA and BF3·OEt2.14A further decrease of basicity of the imine nitrogen as inoximes 11, isoxazolines 12, benzothiadiazines 13, andosazones 14 (Figure 1), due to the presence of a heteroat-om on the nitrogen atom, diminished the reactivitytowards C=N oxidation, and starting materials were re-covered even using 5.0 mmol of MCPBA. Instead the osa-NArHR[O]NArH OR[O] = MCPBA, urea-hydrogen peroxide, Co/O2Figure 1NPhROHO NN OArArNNO2SR1R2N NPh12a: Ar = 4-tolyl12b: Ar = 1-naphthyl13a: R1 = H; R2 = Me13b: R1, R2 = (CH2)31411a: R = H11b: R = MeClSYNLETT 2013, 24, 0053–0056Advanced online publication: 11.12.20120 9 3 6 - 5 2 1 4 1 4 3 7 - 2 0 9 6DOI: 10.1055/s-0032-1317760; Art ID: ST-2012-D0903-L© Georg Thieme Verlag  Stuttgart · New YorkDownloaded by: University of Modena. Copyrighted material.54 L. Troisi et al. LETTERSynlett 2013, 24, 53–56 © Georg Thieme Verlag  Stuttgart · New Yorkzone 14 was oxidized on the amine nitrogen, leading to amixture of different products.15On the contrary, imines containing a heteroatom at the im-ine carbon showed high reactivity towards oxidation. Ox-azolines 15 reacted with 1.1 mmol of peracid leading tothe stable oxaziridines 15 after five hours. Further addi-tion of 1.1 mmol of peracid to 15a led to an unstable N-oxide intermediate which converted into 15b in equilibri-um with the dimeric compound 15c (yield 98%) and/oroxime 15d (R = H, Scheme 5).12Other heterocycles with similar structure exhibit the samebehavior. When 16 was treated with 2.2 mmol of peracid,16b was formed, which converted into the azoxydimericform 16c (yield 98%,16 Scheme 6). These results indicatethat the oxygen bound to the iminic carbon atom increasesreactivity toward oxidation reaction.Imidazoline 17, which contains a nitrogen atom connectedto the imine carbon was transformed (50%) into nitrosocompound 17b and subsequently into azoxydimer 17cwhen treated with 1.1 mmol of MCPBA. It was not possi-ble to isolate oxaziridine 17a and the intermediate form ofthe second oxidation because of their high reactivity. In-stead, 17 led to 17c (yield 99%) when treated with 2.2mmol of peracid (Scheme 7).Only a 50% conversion of 2H-1,2,4-benzothiadiazine de-rivatives 18 and 19,17 structurally similar to the imidazo-lines, into nitroso compounds 18b–19b was observed onreacting with 1.1 mmol of MCPBA, with azoxydimers18c and 19c being isolated as final products. On the otherhand, when 2.2 mmol of peracid were employed the trans-formation to the azoxydimers was complete (99%,Scheme 8).Scheme 2 Oxidative action of the MCPBA toward N-alkyl iminesNArR2R1MCPBA (1.1 mmol)NArR2 OR1MCPBA (1.1 mmol)NArR2 O OR1R1NOArR2ON NR1OOR1CRNOH+1–3 1a–3a1b–3b1c–3c1: R1 = t-Bu, R2 = H, Ar = Ph2: R1 = n-Bu, R2 = H, Ar = Ph3: R1 = n-Bu, R2 = Me, Ar = PhCH2Cl2, 0 °C CH2Cl2, 0 °C2d, 3dScheme 3 Oxidative action of MCPBA toward cyclic iminesN ONN OONOOCH2Cl2, 0 °C CH2Cl2, 0 °CN NOOOO4 4a4b4cNOHO4dMCPBA(1.1 mmol)MCPBA(1.1 mmol)Scheme 4 Oxidative action of MCPBA toward aryl iminesNPhRArNPhRArONArPhOR5–7MCPBA(1.1 or 2.2 mmol)CH2Cl2, 0 °C5a–7a 8–105, 8: R = H, Ar = Ph6, 9: R = H, Ar = 4-ClC6H47, 10: R = Me, Ar = C6H5Figure 2 Projection of compound 18e at 298 KDownloaded by: University of Modena. Copyrighted material.LETTER Oxidation of Different Iminic Bonds 55© Georg Thieme Verlag  Stuttgart · New York Synlett 2013, 24, 53–56Furthermore, nitro compound 18e (90% yield) was isolat-ed on treatment of 18 with 5.5 mmol of MCPBA. Thestructure of 18e was characterized by X-ray crystallo-graphic analysis (Figure 2).18In summary, in this work we have examined the influenceof substituents on the behavior of imines towardsMCPBA. Oxygen, nitrogen, or sulfur, attached to the ni-trogen, render the substrates resistant to oxidation of theπ-bond. On the contrary, a heteroatom or carbon substitu-ent on the imine carbon make the imine double bond morereactive; oxaziridines, amides, oximes, nitroso-, nitro-,and azoxy compounds can be synthesized depending onthe imine/MCPBA stoichiometric ratio.General ProcedureAn excess of MCPBA (1.1 or 2.2 mmol) in CH2Cl2 (3 mL) was add-ed to a solution of the requisite imine (1.0 mmol), dissolved inCH2Cl2 (5 mL), with stirring and cooling (0–5 °C). When reactionwas complete (5–6 h), the excess of m-chloroperbenzoic acid, andthe benzoic acid formed was removed by filtration. The filtrate waswashed twice with a dilute solution of Na2SO3 (5%), then with a so-lution of Na2CO3 (5%), and finally with H2O. After drying over an-hyd MgSO4, the mixture was concentrated in vacuo, and the crudeproduct was purified by column chromatography (silica gel partlydeactivated with Et3N).AcknowledgmentThanks are due to the University of Salento and C.I.N.M.P.I.S.(Consorzio Interuniversitario Nazionale Metodologie e Processi In-novativi di Sintesi) for financial support. We would also like tothank Giuseppe Chita (Istituto di Cristallografia (IC-CNR), ViaAmendola 122/o, 70125, Bari, Italy) for X-ray interpretation.Supporting Information for this article is available online athttp://www.thieme-connect.com/ejournals/toc/synlett.Suporting IformatinSuporting IformatinScheme 5 Oxidative action of the MCPBA toward O-activated cyclic iminesMCPBA (1.1 mmol) MCPBA (1.1 mmol)NORNOOORCH2Cl2, 0 °C CH2Cl2, 0 °CNOOR NOOORNOOOHNO NROOOOOR15 15a15b15c15dR = H or MeScheme 6 Oxidative action of the MCPBA toward O-activated cyclic iminesNONOOON NOOOOOOMCPBA (2.2 mmol)16b16c16CH2Cl2, 0 °CScheme 7 Oxidative action of the MCPBA toward N-activated cycliciminesNNON N NNOOOOOO NNOOOCH2Cl2, 0 °C, 1 h CH2Cl2, 0 °CNNOONNOOO1717b17a17cMCPBA(1.1 mmol)MCPBA(1.1 mmol)Downloaded by: University of Modena. Copyrighted material.56 L. Troisi et al. LETTERSynlett 2013, 24, 53–56 © Georg Thieme Verlag  Stuttgart · New YorkReferences and Notes(1) (a) For a review, see: Harada, T. In The Chemistry of the Carbon–Nitrogen Double Bond; Patai, S., Ed.; Interscience: New York, 1970, 276–293. (b) Rylander, P. N. Best Synthetic Methods: Hydrogenation Methods; Academic Press: London, 1985, 193.(2) Ranu, B. C.; Sarkar, D. C. J. Org. Chem. 1988, 53, 878.(3) (a) Widmer, J.; Keller-Schierlein, W. Helv. Chem. Acta 1974, 57, 657. (b) Emmons, W. D. J. Am. Chem. Soc. 1956, 78, 6208.(4) Lin, Y.; Miller, M. J. J. Org. Chem. 2001, 66, 8282.(5) Damavandi, J. A.; Karami, B.; Zolfigol, M. A. Synlett 2002, 933.(6) Troisi, L.; Rosato, F. Encyclopedia of Reagents for Organic Synthesis; John Wiley and Sons: New York, 2011,; DOI: 10.1002/047084289X.rn01335.(7) Blanc, S.; Bordogna, C. A. C.; Buckley, B. R.; Elsegood, M. R. J.; Bulman Page, P. C. Eur. J. Org. Chem. 2010, 882; and references cited therein.(8) Davis, F. A.; Wei, J.; Sheppard, A. C.; Gubernick, S. Tetrahedron Lett. 1987, 28, 5115.(9) Fabio, M.; Ronzini, L.; Troisi, L. Tetrahedron 2007, 63, 12896.(10) Fabio, M.; Ronzini, L.; Troisi, L. Tetrahedron 2008, 64, 4979.(11) Troisi, L.; Ronzini, L.; Rosato, F.; Videtta, V. Synlett 2009, 1806.(12) Perrone, S.; Pilati, T.; Rosato, F.; Salomone, A.; Videtta, V.; Troisi, L. Tetrahedron 2011, 67, 2090.(13) Nongkunsarn, P.; Ramsden, C. A. Tetrahedron 1997, 53, 3805.(14) An, G.; Kim, M.; Kim, J. Y.; Rhee, H. Tetrahedron Lett. 2003, 44, 2183.(15) (a) Gillis, B. T.; LaMontagne, M. P. J. Org. Chem. 1967, 32, 3318. (b) Witkop, B.; Kissman, H. M. J. Am. Chem. Soc. 1953, 75, 1975. (c) Lynch, B. M.; Pausacker, K. H. J. Chem. Soc. 1953, 2517.(16) Compound 16c: total yield 98%, 179.4 mg;E-Isomer: yield 89.7 mg, 49%, oil; Rf = 0.33 (PE–EtOAc = 9:1). 1H NMR (400.13 MHz, CDCl3): δ = 1.23 (3 H, d, J = 6.5 Hz, CHCH3,), 1.57 (3H, s, CCH3), 1.59 (3 H, s, CCH3), 1.96 (3 H, s, COCH3), 1.97–2.07 (1 H, m, CHaHbCH), 2.47–2.53 (1 H, m, CHaHbCH), 5.02–5.10 (1 H, m, CHCH3). 13C NMR (100.62 MHz, CDCl3): δ = 20.8, 24.5, 27.6, 45.7, 66.8, 86.1, 170.3. FTIR (CHCl3): 2948, 2845, 1730, (C=O), 1270, (NO), 1080 cm–1. ESI-HRMS: m/z calcd for C17H33N2O6 [M + H]+: 361.2333; found: 361.2330.Z-Isomer: yield 89.7 mg, 49%, oil. 1H NMR (400.13 MHz, CDCl3): δ = 1.04 (3 H, s, CCH3), 1.14 (3 H, s, CCH3), 1.20 (3 H, d, J = 6.1 Hz, CHCH3), 1.86 (3 H, s, COCH3), 2.15 (1 H, dd, J = 15.3, 3.1 Hz, CHaHbCH), 2.78 (1 H, dd, J = 15.3, 9.7 Hz, CHaHbCH), 4.84–4.92 (1 H, m, CHaHbCH). 13C NMR (100.62 MHz, CDCl3): δ = 20.5, 21.2, 21.9, 43.2, 67.3, 97.9, 170.5. FTIR (CHCl3): 2950, 2845, 1735, (C=O), 1270, (NO), 1080 cm–1. ESI-HRMS: m/z calcd for C17H33N2O6 [M + H]+: 361.2333; found: 361.2330. (17) Carrozzo, M. M.; Battisti, U. M.; Cannazza, G.; Citti, C.; Parenti, C.; Troisi, L. Tetrahedron Lett. 2012, 53, 3023.(18) (a) Crystal Data for Compound 18eC9H9Cl1N2O5S1, Fw = 292.69, T = 298 K, monoclinic, space group P21/n, a = 11.983(13), b = 7.370(6), c = 15.357(12) Å, α = 90, β = 113.89(5), γ = 90, V = 1240.0 Å3, Z = 4, μ (Mo Kα) = 0.491 mm–1; crystal dimensions 0.3 × 0.2 × 0.06 mm. The X-ray experiments were carried out at r.t. by a Bruker-Nonius KappaCCD diffractometer, using Mo Kα radiation (λ = 0.71073 Å). Data collection was performed by COLLECT (Nonius, 2002. COLLECT and EVAL. Nonius BV, Delft, The Netherlands), cell refinement by DIRAX18b and data reduction by EVAL (Nonius, 2002. COLLECT and EVAL. Nonius BV, Delft, The Netherlands). Absorption effects were corrected by SADABS.18c The crystal structure was solved by SIR201118d and refined by SHELXL-97.18e The H atoms were placed at calculated positions and refined according to a riding model approximation. The software used for preparing the material for publication: WinGX;18f the software used for molecular graphics: Ortep-3.18g Detailed crystallographic data were deposited as CCDC 884506 with the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK.  (b) Duisenberg, A. J. M. J. Appl. Crystallogr. 1992, 25, 92. (c) Sheldrick, G. M. SADABS; University of Göttingen: Germany, 2002. (d) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Siliqi, D.; Spagna, R. J. Appl. Crystallogr. 2007,  40, 609; the updated version of SIR2008 . (e) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112. (f) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837. (g) Farrugia, L. J. J. Appl. Crystallogr. 1997,  30, 565.Scheme 8 Oxidative action of the MCPBA toward S-activated cyclic iminesNNO2S R1R2ClNNO2S R1R2OClNOClO2SN R2OR1NNClO2SNR1 R2OClSO2NR1R2OOO18, 19[O] (1.1 mmol)18: R1 = R2 = Me19: R1–R2 = (CH2)318a, 19a[O] (2.2 mmol)18b, 19b 18c, 19cONO2ClO2SNR1O 18eDownloaded by: University of Modena. Copyrighted material.

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On the oxidation of different iminic bonds by excess of 3-chloroperbenzoic acid

TROISI, Luigino

M. M. Carrozzo

C. Citti

A. Falcicchio

R. Mansueto

F. Rosato

G. Cannazza

Archivio Istituzionale della Ricerca- Università del Salento

On the Oxidation of Different Iminic Bond by Excess of 3-Chloroperbenzoic Acid

https://iris.unimore.it/bitstream/11380/1064406/2/On%20the%20Oxidation%20of%20Different%20Iminic%20Bonds%20by%20Excess%20of%203-Chloroperbenzoic%20Acid.pdf

On the Oxidation of Different Iminic Bond by Excess of 3-Chloroperbenzoic Acid

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